The disclosure relates generally to milling tools, and more particularly, to a milling tool for a portion of a slot in a rotor.
Large industrial machines include a wide variety of large, expensive parts that are stressed during operation. In order to reduce the costs of operating the industrial machines, it is advantageous to extend the lifespan of these parts for as long as safely possible. In order to extend the lifespan of parts, stress relief techniques may applied to create a less stress-inducing structure, e.g., with less sharp corners that may exhibit increased stress. Stress relief techniques may also be advantageous to apply to extend the lifespan of parts already in use in the field.
Turbines include a number of large blades that are coupled to a rotor using slots in the rotor, i.e., mating dovetail connections. During operation, the blades rotate with the rotor as a fluid is forced across the blades, or the blades are forcibly turned to move the fluid. During operation, the blade and rotor connections can be stressed. For example, an end face of the rotor slot, oftentimes a dovetail shape, may include a cooling channel flange that creates a cooling channel at the end face of the slot. A corner at which the flange integrally couples to the end face of the slot may observe high stresses. In order to provide safe operation due to the various stresses, a rotor wheel may be scrapped after, for example, 100,000 hours. Since replacement of a rotor wheel is extremely costly, whatever stress reducing techniques are possible to extend the lifespan of the disk are ideally implemented during manufacturing. However, in some instances, it is possible to apply stress-relieving revisions to a rotor in the field to provide additional stress reduction. Providing stress reducing techniques to rotors in the field, however, presents a number of challenges. For example, it is oftentimes very difficult to reach the structure, such as the afore-described corner of the flange at the end face of the slot. Another challenge is that the revisions that typically need to be completed require precision machining, which is difficult to provide in the field. A further challenge is that where a large number of structures require attention, e.g., 92 blade mounting slots may exist on a turbine rotor, the time requirement and the inherent costs to provide the stress relief techniques to the entire structure can be very high.